Title: Study of duality in the transition region at Jlab

Abstract

Inclusive double spin asymmetries obtained by scattering polarized electrons off polarized protons and deuterons have been analyzed to address the issue of quark-hadron duality in the polarized spin structure functions g^p_1 and g^d_1. A polarized electron beam, solid polarized NH_3 and ND_3 targets and the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B were used to collect the data. The resulting g^p_1 and g^d_1 were averaged over the nucleon resonance energy region (M < W < 2.00 GeV), and three lowest lying resonances individually for tests of global and local duality.

I will discuss recent results from Jefferson Lab on the measurement of inclusive spin structure functions in the nucleon resonance region using polarized ammonia NH{sub 3} and polarized {sup 3}He targets. Preliminary results on the first moment of g{_}1(x,Q{sup 2}) for protons, and the generalized Gerasimov-Drell-Hearn integral for neutrons are presented. In addition, first double polarization data on exclusive electroproduction of pi{sup +} for polarized protons will be discussed.

The Electron-Ion Collider (EIC) is envisioned as the next-generation US facility for exploring the strong interaction. The Medium-energy EIC (MEIC) is the first stage of the EIC at Jefferson Lab (JLab). It's aimed at mapping the spin and spatial structure of the quark and gluon sea in the nucleon, understanding the emergence of hadronic matter from color charge, and probing the gluon fields in nuclei. A full-acceptance detector is designed to measure the complete final state. Its interaction region allows spectators tagged with high resolution to catch all nuclear and partonic target fragments. The combination of a high luminosity, polarizedmore » lepton and ion beams, and detectors fully integrated with the accelerator will allow MEIC to be a unique opportunity to make breakthroughs in the study of nucleon structure and QCD dynamics.« less

The hypernuclear physics program at JLAB requires an electron beam with small transverse size (sigma {approx} 100 {micro}m) and an upper limit on the RMS energy spread of delta E / E < 3 x 10{sup -}5. To measure and monitor these parameters, a beam size and energy spread measurement system has been created. The system consists of a set of wire scanners, Optical Transition Radiation (OTR) detectors, and Synchrotron Light Interferometers (SLI). The energy spread is measured via a set of wire scans performed at specific locations in the transport line, which is an invasive process. During physics operationmore » the energy spread is monitored continuously with the OTR and/or the SLI. These devices are noninvasive [or nearly non-invasive in the case of OTR] and operate over a very wide range of beam energies (1.6 GeV) and currents ({approx}100 {micro}A down to few {micro}A). All components of this system are automated in an EPICS accelerator control environment. The paper presents our operational experience with the beam size and energy spread measurement system and its maintenance.« less

A fundamental issue in hadron physics is which degrees of freedom are appropriate to describe exclusive reactions at experimentally accessible momentum transfers, and how are models at low, medium and high Q{sup 2} related? Constituent quark models (CQM) appear to work well at the low Q{sup 2} limit, and it is widely believed that valance pQCD will be valid in the limit of high Q{sup 2}. How far the validity of these models extend in Q{sup 2} is still an open question. Many exclusive reactions exhibit constituent scaling behavior at moderate Q{sup 2} ( few GeV{sup 2}/c{sup 2}) which ismore » interpreted by some [1] as the onset of perturbative QCD. Others [2] argue that the observed scaling is not a manifestation of pQCD, and that at the experimentally accessible range of Q{sup 2} exclusive reactions are explained primarily by soft Feynman mechanism. Recently[3][4], there have been promising developments in bridging the high and low Q{sup 2} extremes for exclusive reactions in terms of a quark-parton description of exclusive reactions In this approach the perturbative hard part of the reaction, which is calculable, is isolated from the non-perturbative soft, physics which is parameterized in terms of non-forward parton distributions (NFPD). These NFPD's are generalizations of the usual parton non-spin and spin distribution functions obtained in unpolarized and polarized deep inelastic inclusive scattering, and in fact reduce to them in the limit of forward scattering. An attractive aspect of this approach is that the same NFPD can be carried over to a variety of exclusive reactions which involve the same set of hadrons, and can be constrained in a number of different experiments which are discussed in these proceedings.« less